Special molecular testing on blood specimens done by the Centers for Disease Control and Prevention found that the patients were infected with strains of hepatitis C closely related to infections linked to David Kwiatkowski, state health officials said Friday.

The new cases bring to five the number of people in Maryland believed infected by Kwiatkowski.

Kwiatkowski, who worked as a traveling radiologic technician in hospitals across the country, is accused of injecting himself with stolen narcotics-filled syringes and leaving the contaminated needles, filled with saline, to be used on other patients.

Hopkins officials said in a statement that Kwiatkowski was employed by staffing agency Medical Solutions, a company Hopkins used to hire contract medical technicians. Hopkins said its contract with the company required "rigorous vetting" of employees that includes a criminal background check, credentials and licensure verification, health and drug screening and two references.

"Johns Hopkins was assured that the process was followed," the statement said. "In this case, none of the information that Medical Solutions provided about this health care worker suggested a history of drug diversion or any other criminal activity," the medical institution said in a statement.

One other Maryland patient, treated at the Baltimore VA, has also been tried to a hepatitis strain related to Kwiatkowski. The Baltimore VA has not released the name of the patient, but Vietnam veteran Linwood Nelson and his lawyer have said he believes he contracted the disease while receiving treatment at the Baltimore VA Medical Center while Kwiatkowski worked there.

More than 1,700 patients at four Maryland hospitals have been notified to get tested for hepatitis C because they had undergone a procedure in which Kwiatkowski might have been involved. The technician worked at the Baltimore VA Medical Center from May to November 2008, at Southern Maryland Hospital between December 2008 and February 2009, at Johns Hopkins Hospital between July 2009 and January 2010, and at Maryland General Hospital from January to March 2010.

Kwiatkowski has pleaded not guilty to charges that included tampering with a consumer product and obtaining controlled substances by fraud.

According to the FBI, Kwiatkowski learned that he was infected with hepatitis C in May, though investigators have uncovered evidence that he had the disease since at least June 2010. Hepatitis C is a blood-borne disease that attacks the liver.